We are performing theoretical and empirical studies of the kinetics of transmission and the population dynamics of conjugative and mobilizable nonconjugative plasmids. The theoretical portion of this work involves the development and analysis of mathematical models of these systems. The empirical portions involve experiments with batch and chemostat cultures of E. coli and some of its R and F plasmids. The major goals of these investigations are to 1) determine whether sets of differential equations with relatively few parameters can be used as realistic and predictive models of the transfer kinetics and population dynamics of plasmids in liquid cultures of bacteria and 2) to ascertain the conditions for the establishment and maintenance of plasmids in bacterial populations. We are also doing theoretical and experimental studies of the kinetics of infection and lysogeny of temperate bacterial viruses and the population dynamics of these types of phage. The experimental portions of these investigations are with the phage P1 with batch and chemostat populations of E. coli. The primary goals of these studies are 1) to develop realistic models for the kinetics of infection and lysogeny and population dynamics of temperate phage, 2) to ascertain the conditions under which temperate phage could become established and would be maintained in bacterial populations and 3) to ascertain the selective pressures leading to and maintaining temperature rather than virulent phage life cycles.